Magnetic carrier and two-component developer

Abstract

The present invention is a magnetic carrier that has a magnetic carrier core and a resin coat layer, wherein the resin coat layer contains a coat resin A and a coat resin B, the coat resin A is a polymer obtained by polymerization of a (meth)acrylate ester monomer that has an alicyclic hydrocarbon group, the coat resin B is a polymer obtained by polymerization of (meth)acrylic monomer and has a polar group and an acid value of 4.0 to 50.0 mg KOH/g, the content of the coat resin A is 10 to 90 mass %, the content of the coat resin B is 10 to 90 mass %, and an acid value of the resin component in the resin coat layer is 1.0 to 10.0 mg KOH/g.

What is claimed is: 
     
       1. A magnetic carrier having a magnetic carrier core and a resin coat layer formed on the surface of the magnetic carrier core, wherein
 the resin coat layer contains a resin component comprising a coat resin A and a coat resin B; 
 the coat resin A is a polymer having an acid value from 0 to 3.0 KOH/g and that is obtained by polymerization of a (meth)acrylate ester monomer that has an alicyclic hydrocarbon group; 
 the coat resin B is a polymer comprising a polar group and having an acid value from 4.0 to 50.0 mg KOH/g, that is obtained by polymerization of (meth)acrylic monomer; 
 the coat resin A is contained in the resin coat layer at from 10 to 90 mass % with reference to the mass of the resin component in the resin coat layer; 
 the coat resin B is contained in the resin coat layer at from 10 to 90 mass % with reference to the mass of the resin component in the resin coat layer; and 
 the acid value of the resin component in the resin coat layer is from 1.0 to 10.0 mg KOH/g. 
 
     
     
       2. The magnetic carrier according to  claim 1 , wherein coat resin A is a polymer obtained by copolymerization of a macromonomer, and a (meth)acrylate ester monomer that has an alicyclic hydrocarbon group, and
 the macromonomer is obtained by polymerization of at least one monomer selected from the group consisting of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. 
 
     
     
       3. The magnetic carrier according to  claim 1 , wherein a minimum value of a storage elastic modulus (G′) of the resin coat layer at from 70° C. to 100° C. is from 7.0×10 7  Pa to 1.0×10 9  Pa, and
 a minimum value of a loss elastic modulus (G″) of the resin coat layer at rom 70° C. to 100° C. is from 1.0×10 6  Pa to 1.0×10 8  Pa. 
 
     
     
       4. The magnetic carrier according to  claim 1 , wherein the acid value of the resin component in the resin coat layer is from 1.0 mg KOH/g to 5.0 mg KOH/g. 
     
     
       5. A two-component developer having a toner and a magnetic carrier, wherein the magnetic carrier has a magnetic carrier core and a resin coat layer formed on the surface of the magnetic carrier core;
 the resin coat layer contains a resin component comprising a coat resin A and a coat resin B; 
 the coat resin A is a polymer having an acid value from 0 to 3.0 mg KOH/g and that is obtained by polymerization of a (meth)acrylate ester monomer that has an alicyclic hydrocarbon group; 
 the coat resin B is a polymer comprising a polar group and having an acid value from 4.0 to 50.0 mg KOH/g, that is obtained by polymerization of (meth)acrylic monomer; 
 the coat resin A is contained in the resin coat layer at from 10 to 90 mass % with reference to the mass of the resin component in the resin coat layer; 
 the coat resin B is contained in the resin coat layer at from 10 to 90 mass % with reference to the mass of the resin component in the resin coat layer; and 
 the acid value of the resin component in the resin coat layer is from 1.0 to 10.0 mg KOH/g. 
 
     
     
       6. The two-component developer according to  claim 5 , wherein coat resin A is a polymer obtained by copolymerization of a macromonomer, and a (meth) acrylate ester monomer that has an alicyclic hydrocarbon group, and
 the macromonomer is obtained by polymerization of at least one monomer selected from the group consisting of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. 
 
     
     
       7. The two-component developer according to  claim 5 , wherein a minimum value of a storage elastic modulus (G′) of the resin coat layer at from 70° C. to 100 20   C. is from 7.0×10 7  Pa to 1.0×10 9  Pa, and
 a minimum value of a loss elastic modulus (G″) of the resin coat layer at from 70° C. to 100° C. is from 1.0×10 6  Pa to 1.0×10 8  Pa. 
 
     
     
       8. The two-component developer according to  claim 5 , wherein the acid value of the resin component in the resin coat layer is from 1.0 mg KOH/g to 5.0 mg KOH/g.